Spacecraft based applications of all kinds have increased over the last years. In particular, the interest for micro- and nano-satellites has increased, since the costs for launching can be significantly reduced by launching a large number of spacecraft simultaneously. This is achieved by reducing mass and volume of spacecraft.
One particular field in space science concerns propulsion and maneuverability of the spacecraft or parts thereof. For microspacecraft, the forces needed to perform certain propulsion and/or maneuvers are relatively limited, whereby also the propulsion systems themselves can be made very small. Typical forces are in the μN to mN ranges. One particular approach for propulsion is to use the momentum of gas streaming out from an opening. This approach is suitable for precision control of advanced space systems as well as a primary propulsion method for miniaturized satellites, where low mass, volume and power consumption are important driving criterions.
In a traditional setup, a cold gas thruster is utilized. Gas in a high-pressure tank is allowed to escape through a stagnation chamber and a nozzle. The existence of the nozzle increases the speed, and thereby the momentum, of the gas exiting the gas thruster. A recoil action will drive the thruster, and any device attached thereto in an opposite direction.
In the Swedish patent SE 527 154, a gas thruster system is disclosed, where the gas, when passing the stagnation chamber is heated by internal heaters before entering into the nozzle. Since the momentum of the gas increases by the square root of the gas temperature, a much higher propulsion efficiency of the stored gas can be obtained. Furthermore, by using the laminar flow of the gas through the stagnation chamber, a very high temperature can be achieved in the middle of the gas stream while keeping the gas coming into direct contact with the chamber and nozzle walls at a lower temperature. Mean gas temperatures can in such a way be allowed to exceed the maximum operation temperature of the chamber and nozzle walls. In one embodiment of SE 527 154, a cylindrical heater coil of diamond-like carbon (DLC) has been used. The coils were manufactured by use of laser chemical vapour deposition techniques.
One problem with high-efficiency gas thruster systems according to prior art is that the complexity for manufacturing and mounting heaters is large. In order, not to reduce the reliability of the operation of such systems, the manufacturing becomes very time consuming as well as expensive. Another problem with high-efficiency gas thruster systems according to prior art is that the heater arrangements are sensitive to wear and/or corrosion. Furthermore, there is a general need for further improving robustness as well as efficiency.